Brazilian Journal of Development 22110 ISSN: 2525-8761 A simple and cheaper solution to calibrate microcomputer time base with NIST totalizer method Uma solução simples e mais barata para calibrar a base de tempo do microcomputador com o método totalizador NIST DOI:10.34117/bjdv7n3-089 Recebimento dos originais: 08/02/2021 Aceitação para publicação: 05/03/2021 Daniel da Silva Quaresma Mestrado Observatório Nacional Endereço: Rua General José Cristino, 77 - São Cristóvão - Rio de Janeiro - RJ - CEP: 20921-400 E-mail: [email protected] Ricardo José de Carvalho Doutorado Observatório Nacional Endereço: Rua General José Cristino, 77 - São Cristóvão - Rio de Janeiro - RJ - CEP: 20921-400 E-mail: [email protected] Antônio Eduardo de Oliveira Doutorado Instituto de Radioproteção e Dosimetria Endereço: Av Salvador Allende, 3.773 - Barra da Tijuca - Rio de Janeiro - RJ - CEP - 22783-127 E-mail: [email protected] Carlos José da Silva Doutorado Instituto de Radioproteção e Dosimetria Endereço: Av Salvador Allende, 3.773 - Barra da Tijuca - Rio de Janeiro - RJ - CEP - 22783-127 E-mail: [email protected] Akira Iwahara Doutorado Instituto de Radioproteção e Dosimetria Endereço: Av Salvador Allende, 3.773 - Barra da Tijuca - Rio de Janeiro - RJ - CEP - 22783-127 E-mail: [email protected] Brazilian Journal of Development, Curitiba, v.7, n.3, p. 22110-22121 mar 2021 Brazilian Journal of Development 22111 ISSN: 2525-8761 José Ubiratan Delgado Doutorado Instituto de Radioproteção e Dosimetria Endereço: Av Salvador Allende, 3.773 - Barra da Tijuca - Rio de Janeiro - RJ - CEP - 22783-127 E-mail: [email protected] José Guilherme Pereira Peixoto Doutorado Instituto de Radioproteção e Dosimetria Endereço: Av Salvador Allende, 3.773 - Barra da Tijuca - Rio de Janeiro - RJ - CEP - 22783-127 E-mail: [email protected] ABSTRACT Normally, laboratories that need traceability of time quantity in measurements, find high cost and complex infrastructure to collect traceable time measurements and automation software. This paper shows the calibration of microcomputers in LNMRI laboratory, using a simple method proposed by Special Publication NIST 960-12, with a unique reference counter with an external time base by the CSAC cesium frequency standard and a virtual stopwatch that can be download on the internet. The totalizer method is a simple way to calibrate time offset dt/t, and the results show that the microcomputers can be used how a time base reference in measurements that required dimensionless fractional time uncertainty until microseconds for a second. Keywords: Traceability, Totalizer method, Microcomputer, Time offset. RESUMO Normalmente, os laboratórios que precisam de rastreabilidade da quantidade de tempo nas medições encontram alto custo e infraestrutura complexa para coletar medições de tempo rastreáveis e software de automação. Este artigo mostra a calibração de microcomputadores no laboratório do LNMRI, utilizando um método simples proposto pela Publicação Especial NIST 960-12, com um contador de referência exclusivo com base de tempo externa pelo padrão de frequência de césio CSAC e um cronômetro virtual que pode ser baixado no Internet. O método totalizador é uma maneira simples de calibrar o deslocamento de tempo dt / t, e os resultados mostram que os microcomputadores podem ser usados como uma referência de base de tempo em medições que requerem incerteza de tempo fracionário adimensional de até microssegundos por segundo. Palavras-chave: Rastreabilidade, Método Totalizer, Microcomputador, Time offset. 1 INTRODUCTION The Instituto de Radioproteção e Dosimetria (IRD) is the national reference to standardize quantities of Ionizing Radiation, and the Observatório Nacional (ON) is the reference in Time and Frequency. Both of Institutes have this delegated mission, in the interest of Country, by Instituto Nacional de Metrologia, Qualidade e Tecnologia Brazilian Journal of Development, Curitiba, v.7, n.3, p. 22110-22121 mar 2021 Brazilian Journal of Development 22112 ISSN: 2525-8761 (INMETRO) that is the Legal Authority in Metrology in Brazil, officially recognize by BIPM with that mission. In this way, the research to solutions in Ionizing Radiation and Time and Frequency Metrology is its priority of the group. Thus, with a long history, in 1912, with 16 representatives, including Brazil, was created the BIH (International Bureau of Time) [1]. In 1921, at the 6th metro convention, the Bureau International des Poids et Mesures (BIPM) extended the scope and responsibilities in other fields of action and the advisory committee for electricity (CCE, and currently CCEM) was created [2]. In 2005, the CCTF (Time and Attendance Advisory Committee), the working group was created where the main objectives are to develop and propose standards for specific documentation. Its provide discussion forums, to interact with BIPM on issues related to International Atomic Time (TAI) and to encourage, facilitate and provide help for the direct comparison between primary frequency patterns and the construction of new standards [3]. Currently, Brazil participates in the CCTF as an official observer through the National Observatory (ON / MCTIC), through the designation of the National Institute of Metrology, Quality, and Technology (INMETRO / MDIC) [4]. The details of the time quantity history show that the time traceability in measurements is not quite trivial, because the cost of apparatus is so not attractive, and the instruments accessories to collect data require more infrastructure in software and training to development. So, was proposed a simple way to traceable the internal time base of the microcomputers, for specific applications, based on a known method, and cheaper to calibrate lots of microcomputers in a laboratory net, where a unique setup can transfer traceability. 2 MATERIALS The time and frequency standard CSAC (Chip-Scale Atomic Clock) is a reference generation system with 1 PPS outputs in 5 V and 10 MHz in alternating high square wave. The system has low power consumption less than 125 mW and is manufactured in the standard board where the chip contains a TCXO internal quartz oscillator and the CSAC module with a cesium 133 source, the same chemical element of the definition of the second in the SI. The laser camera for detecting the transition of 9,192,631,770 cycles per second, in miniature configuration, which controls the quartz operating point. Brazilian Journal of Development, Curitiba, v.7, n.3, p. 22110-22121 mar 2021 Brazilian Journal of Development 22113 ISSN: 2525-8761 The system comes with control software and RS-232 serial interface to the user, multi-connector board for parameter configuration, the possibility of synchronization and external discipline via another reference standard or GPS, offset adjustment and monitoring of operational data such as temperature, laser operating point, drift and other parameters necessary for the operation of the equipment. Figure 1 below shows the overview of the board and the CSAC module. Figure 1 – Circuit board for mounting the CSAC module [5] The main output signal of the CSAC is provided by the TCXO quartz oscillator, which is continuously compared and corrected by the hyperfine frequency of the cesium atoms which is 9,192,631,770 Hz. Figure 2 shows the block diagram of the CSAC. Figure 2 – CSAC Time and Frequency Pattern Block Diagram [5] AUTOMED is the name of the multiplexer, which is the automatic time interval measurement system used in the Time Service Division (DISHO), one pulse per second (1 PPS) time and frequency standard. The system uses an universal time interval counter SR620 to measure the difference between the pulses of 1 PPS, a switching module of the various 1 PPS signal inputs, a microcomputer for signal processing and a graphical interface for user interaction. The measurements are performed with time intervals τ0 = 60 s for each measured standard, the time difference sampling of each measured standard is in 60 s intervals. The Brazilian Journal of Development, Curitiba, v.7, n.3, p. 22110-22121 mar 2021 Brazilian Journal of Development 22114 ISSN: 2525-8761 standard was compared with the reference 1 PPS signals of the Brazilian Atomic Time Scale (UTC(ONRJ)) and the T130 (cesium standard used in the calibration laboratory). The system has two dedicated calibration channels, CAL01 and CAL02, and time difference data is stored in .txt files in a folder on a data server. The TSC5110A is a meter that uses the time difference technique with dual DTDM mixer [6], of frequency signals provided by time and frequency patterns. The system receives the input signals on channels A and B, one of the respective channels being the frequency reference and the other channel for the equipment to be tested (DUT), figure 3. Figure 3 – TSC5110A [6] Measurements can be performed at τ0 = 1 s (1 sample per second) and τ0 = 10 ms (100 samples per second). The equipment display allows plotting the Allan deviation data (frequency stability), phase and frequency measurements of the standard under test with respect to the reference. The collected data is transfer to the microcomputer via serial port (1 sample per second) and stored in .txt format, ordered by MJD on each measurement day. The collection of 100 samples per second is done through TCP-IP cable and stored in a .txt format file. The block diagram is shown in Figure 4. Figure 4 – Block diagram of the phase data acquisition in the dual-mixer time difference measurement method - DTDM [6] Brazilian Journal of Development, Curitiba, v.7, n.3, p. 22110-22121 mar 2021 Brazilian Journal of Development 22115 ISSN: 2525-8761 The same frequency signals at inputs A and B are combined with a reference offset (mixer) to eliminate the influence of the offset fluctuation of the two inputs, and the contribution of the reference signal is canceled in the process of treating the output signal. The PM6681 is a counter totalizer that was utilized with CSAC time base to calibrate the microcomputer´s time base.